Conventional photovoltaic cells are more efficient at higher sun magnifications, if the cells can be kept cool. Cooling becomes very problematic at magnifications of over, say, 20 suns, so a device which provides sun multiplications in the range of, say, 7 to 20 suns, holds promise as a way to hold down cell costs and provide improved efficiency over conventional solar panels operating at 1 sun intensity.
Compound parabolic concentrators (CPCs) are well known and are the subject of numerous patents to Roland Winston. For example, see U.S. Pat. No. 4,045,246 and U.S. Pat. No. 4,003,638, the disclosures of which are incorporated by reference. In one form, the collectors comprise a long reflectively lined trough having an interior surface designed to accept incoming sunlight over a range of incoming angles and concentrate it to a receiver positioned in the bottom of the trough. Typically, the troughs provide sunlight to the bottom of the trough at 2 to 6 suns intensity.
One of the drawbacks to the use of a CPC which operates to concentrate the sun to, say, 6×, which would provide greater cell efficiency, and savings in cell costs, is their size. A 6×CPC trough having a 6 inch outlet and a 36 inch inlet would have a height of about 8 feet. In order to provide, say, 2000 watts of peak power, the trough would need a length of about 60 feet. A more compact device would be desirable. A device having a reduced sail area would be desirable. A device capable of practical operations at higher magnification would also be desirable.